The present invention relates to an exposure device used in a silver salt photographic type copying apparatus.
Silver salt photographic type copying machines can provide high quality copies compared to electronic copying apparatuses. Silver salt copying apparatuses are classified into two or more groups, including: a slit exposure type and a camera type corresponding to the exposure system; a diffusion transfer type using diffusion transfer photographic materials; a direct positive image forming type using direct positive photographic materials; and a reversal developing type using reversal films corresponding to the image forming process.
Diffusion transfer type copying apparatuses use two separate diffusion transfer photographic materials: a negative or photosensitive material, in which a latent image is created as a result of exposure; and a positive or image-receiving material where the positive image is formed.
One such diffusion transfer type copying apparatus is disclosed in Japanese Patent Unexamined Publication No. 59-204042, in which a roll-shaped negative or photosensitive material contained in a magazine is withdrawn and cut into sheets of a predetermined length. Each photosensitive sheet is placed and held flat on an exposure stage in order to be exposed. After exposure, the photosensitive material is superimposed onto a positive or image-receiving material in the form of a sheet withdrawn from a cassette, and while superimposed is passed through a developing reagent and then held in a storing chamber for a while for diffusion transfer processing. Thereafter, the image-receiving sheet is peeled away from the photosensitive sheet upon the completion of diffusion transfer processing. A positive transfer image is formed on the image-receiving sheet. After being washed and dried the image-receiving sheet is removed from t he copying apparatus.
A camera type copying apparatus is known, such as that in Japanese Unexamined Published Patent Application No. 61-138 955. in which a roll of photosensitive material and a sheet of image-receiving material are used.
The conventional diffusion transfer type copying apparatus is deficient in that a large area is needed for the exposure stage, because a photosensitive sheet to which the photosensitive material is cut off is placed on an exposure stage and exposed either by a slit exposure light or by a frame exposure. Further, as the size of the photosensitive sheet increases it becomes difficult to keep the photosensitive sheet flat on the exposure stage.